Frequency measuring apparatus for controlling the temperature of a glass fiber forming apparatus

ABSTRACT

THIS INVENTION RELATES TO AN APPARATUS FOR ISSUING STREAMS OF MOLTNE GLASS TO BE ATTENUATED INTO FIBERS. THE TEMPERATURE OF THE MOLTEN GLASS IS SENSED BY A DEVICE GENERATING A FREQUENCY SIGNAL WHICH VARIES IN PROPORTION TO TEMPERATURE VARIATION OF THE MOLTEN GLASS. A KNOWN PERIOD OF THE CYCLIC VARIATION OF THE FREQUENCY SIGNAL IS SELECTED AND A COUNTER COUNTS A PREDETERMINED HIGHER FRE-   QUENCY RATE DURING THE KNOWN PERIOD TO PROVIDE A MEASURE OF THE TEMPERATURE OF THE GLASS. THE AMOUNT OF HEAT SUPPLIED TO THE GLASS IS CONTROLLED IN RESPONSE TO THE OUTPUT OF THE COUNTER.

June 1,. 1971 W. C. TRETHEWEY FREQUENCY MEASURING APPARATUS FORCONTROLLING THE TEMPERATURE Original Fued Nov. 5. 1966 FEEDER TE MP TIMEOF A GLASS FIBER FORMING APPARATUS 4 Shebts-Shoot 1 D6 v --X; Y x.

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FREQUENCY MEASURING APPARATUS FOR CONTROLLING THE TEMP Emma OF A GLASSFIBER FORMING APPARATUS Original Fuea Nov. 3, 1966 4 Shoots-Shoot 3ATTORNEYS June 1, 1971 w. c. TRETHEWEY 3,532,293

FREQUENCY MEASURING APPARATUS FOR CONTROLLING THE TEMPERATURE OF A GLASSFIBER FORMING APPARATUS Original Fzlod Nov. 5. 1966 4 Sheets-Shoot 4.

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FRE UENCY 5| NAL ATTORNEYS United States Patent Ofice Patented June 1,,1971 FREQUENCY MEASURING APPARATUS FOR CON- TROLLING THE TEMPERATURE OFA GLASS FIBER FORMING APPARATUS William C. Trethewey, Newark, Ohio,assignor to Owens- Corning Fiberglas Corporation Original applicationNov. 3, 1966, Ser. No. 591,906, now Patent No. 3,467,325, dated Sept.16, 1969. Divided and this application Apr. 7, 1969, Ser. No. 832,528

Int. Cl. C03b 37/02 U.S. Cl. 65-11 3 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to an apparatus for issuing streams of moltenglass to be attenuated into fibers, The temperature of the molten glassis sensd by a device generating a frequency signal which varies inproportion to temperature variation of the molten glass. A known periodof the cyclic variation of the frequency signal is selected and acounter counts a predetermined higher frequency rate during the knownperiod to provide a measure of the temperature of the glass. The amountof heat supplied to the glass is controlled in response to the output ofthe counter.

This is a division of co-pending application Ser. No. 591,906, filedNov. 3, 1966, now Pat. 3,467,325, granted Sept. 16, 1969.

This invention relates generally to frequency measuring apparatus andmore particularly to the use of such frequency measuring apparatus incondition sensing apparatus which may be utilized for sensing a variablecondition and controlling the variable condition. Further, the inventiveconcept is particularly applicable in fiber pro ducing apparatus.

As the instrumentation approach in measurement and control of variables,apparatus, and processes has grown more sophisticated, the requirementsfor accuracy in such instrumentation approaches have also increased toprovide a closer quality check on the goods being produced and on theprocesses being used. More sensitive frequency measuring apparatus andthe novel inventive concepts that spring from the use of more sensitivefrequency measuring devices lead to better products and processes. Forexample, it is well known that thermoplastic materials such as glass canbe drawn into continuous fibers by attenuation of streams from a feederassociated with a molten body of this material. The flowing material isattenuated in the process into individual fibers which are usuallygathered into a strand under the influence of pulling forces exerted bya winder which collects the strand into a package. The strand in suchinstances is usually wound on a collection tube mounted on a rotatingcollet of the winder and may be collected at linear speeds in the orderof 15,000 to 20,000 feet per minute or more.

In manufacturing fibers in this manner, the goal has been to producefibers which are closely similar in diameter and individual fibers ofuniform diameter throughout their lengths. If production of fibers ofsuch uniformity could be attained, the strand yardage per pound of glasssupplied from the feeder would be consistently uniform and much would bedone to promote consumer reliance upon the product quality when strandor fiber diameters are specified.

On collection of strands into a package, however, a gradual build-up ofthe package occurs in the usual packaging cycle of, for example, six tothirty minutes, such that for a given speed of the collection tube, thelinear speed of attenuation is in effect gradually and substantiallyuniformly increased to a maximum linear speed toward the end of thepackaging cycle. In other words, at the start of a packaging cycle, thelinear speed of attenuation of the fiber from the feeder is determinedby the outer diameter of the bare collection tube, but as the build-upof the package occurs, the speed of attenuation instead becomesdependent upon the outer diameter of the top layers of strand in thepackage. When viewed on an over-all basis, the linear speed ofattenuation increases gradually from a minimum at the beginning of apackaging cycle to a maximum at the end of a packaging cycle when thepackage is completed. Under fixed conditions of temperature of the glasssupplied from the feeder, the diameter of fibers collected into thestrands being wound is correspondingly undesirably diminished because ofthis increase in speed. Consequently, the yardage per unit weight ofglass being collected also varied dependent upon whether it is collectedat the beginning or the end of the package.

It has been discovered that when one of the fiber-forming factors suchas the temperature of the thermoplastic material emitted from the feederor the rotational speed of the winder which collects the strand into apackage is programmed or varied at a patterned rate matched to thevariation in linear speed of attenuation, that the fiber diameter can bemaintained more exactingly uniform. When utilizing such variableconditions as control factors, such as glass temperature or windingspeed, it then becomes incumbent upon the control apparatus to do sowith the highest degree of accuracy possible in order to attain the bestresults.

Accordingly, it is an object of this invention to provide improvedfrequency measuring apparatus which is adapted to provide readoutindications of the frequency or other variable conditions beingmeasured, and which is also adapted to provide a signal which is ameasure of the variable condition and which can be utilized to correct aprogrammed variation of the condition.

It is a further object of this invention to provide condition sensingapparatus which may be utilized to control the apparatus providing thevariable condition.

A still further object of this invention is to provide fiber producingapparatus in which a variable condition is being controlled by aprogrammed approach, which condition may be sensed and the sensingresults utilized to correct the preselected programmed approach,

In effecting the above objects the invention features frequencymeasuring apparatus which comprises means for sampling a frequencysignal to be measured, means for selecting a predetermined period of thesampled frequency signal, and counter means responsive to the selectingmeans which is adapted to count at a predetermined frequency during theselected period of the sampled frequency. The counting frequency ishigher than the frequency of the signals being measured and thus thetotal count accumulated by the counter at the end of a selected periodis a measure of the frequency. The selecting means may include meansresponsive to a reversal in polarity of the frequency being measured.The apparatus may further include means for selecting a secondpredetermined period of the sampled frequency signal. The counter meansmay be made responsive to the second selecting means and operative tocount during the second selective period. Means may then be utilized forcomparing the total counts in the first-mentioned and the second periodsto determine the accuracy of the frequency measuring apparatus, orwhether the first count repre sented a full predetermined period.

The invention also features condition sensing and controlling apparatusWhich comprises means for sensing a variable condition and generating afrequency signal in which the frequency varies in proportion to thevariation of the condition being sensed. Such apparatus includes meansfor selecting a predetermined period of the frequency signal and countermeans responsive to the selecting means adapted to count at apredetermined frequency during the selected period of the sensedfrequency. As above, the counting frequency is higher than the frequencyof the frequency signal being measured, the frequency count being ameasure of the variable condition being sensed. As examples of variableconditions that may be sensed and/or controlled, there are illustratedherein embodiments sensing the speed of the winder collecting fibersonto a package, the temperature of a feeder containing moltenthermoplastic materials, fluid flow, particle flow, and pressure. Inorder to control the variable conditions, means may be utilized forcomparing the sensed frequency count with a preselected standard andmeans responsive to the comparing means may be utilized for altering thevariable condition, whether altering a preselected programmed approachor altering directly the variation of the condition.

Specifically, the invention is illustrated in detail in fiber producingapparatus which comprises means for supplying a plurality of streams ofmolten fiber-forming material, a winder collet for attenuating thestreams into continuous fibers and for collecting said fibers into apackage and motor means for rotationally driving the collet.

If the fiber producing apparatus includes motor control means havingmeans for generating frequency signals to regulate the speed of themotor means, variable driving means connected to drive the frequencygenerating means, and means for providing preselected programmedauxiliary signals matched to the build-up rate of the package on thecollet to vary the connection of the variable driving means to thefrequency generating means, then there may be utilized means for sensingand measuring the frequency generated by the frequency generating means.By comparing the measured frequency with a frequency standard desired atthe time of sensing measuring, a signal is produced for correcting theauxiliary signals in accordance with the results of the frequencycomparison,

If, on the other hand, the fiber producing apparatus includes atemperature measuring device in a control means arranged to supplysignals to regulate a heating means for the feeder means to maintain agiven temperature of a molten body in the feeder means, then means maybe utilized for supplying programmed auxiliary signals to the controlmeans for variation of the temperature of the molten body at a ratematched to variations in the rate of attenuation of the streams inresponse to package build-up. In this instance, means for sensing thetemperature of the molten body and generating a frequency signal inwhich the frequency of the signal varies in proportion to the variationof the temperature being sensed may be used. The frequency signal may bemeasured, preferably by a counter means as described hereinbefore whichis responsive to a selecting means adapted to select a predeterminedperiod of the signal. The measured frequency may be compared with apreselected standard and means may be utilized which are responsive tothe comparing means for effecting correction of the control means or thepreselected auxiliary programmed signal supplying means.

Other objects, advantages and features of this invention will becomeapparent when the following description is taken in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a general layout of apparatus for producing continuousglass fibers;

FIG. 2 is a front elevational view of the general layout of apparatusshown in FIG. 1;

FIG. 3 illustrates in graphic form the winding motor speed-timecharacteristics that are desirable for optimum fiber diameter control;

FIG. 4 is a block diagram illustration of a circuit which may be usedfor control of winder motor speed in collecting the fibers onto apackage;

FIG. 5 illustrates in graphic form the desirable feeder temperature-timecharacteristics for optimum diameter control;

FIG. 6 is a block diagram illustration of a circuit which may be usedfor control of the electrical current supplied to the feeder of theapparatus of FIGS. 1 and 2;

FIG. 7 illustrates variable condition measuring apparatus of thisinvention as applied to fluid flow;

FIG. 8 illustrates variable condition measuring apparatus of thisinvention as applied to particle flow, and

FIG. 9 illustrates variable condition sensing apparatus as applied tothe measurement of pressure.

Although the invention is herein exemplified in specific detail byreference to glass fiber production, it will be apparent in view of thedisclosure that it has application to production of fibers of othermaterials as well. Further, although the variable conditions shown assubjects of measurement and control are specific uses of the inventionherein disclosed, it is to be noted that all embodiments areillustrative only and not limiting in any sense with respect toapparatus, process, product or other use of the invention as disclosedherein.

Turning to the drawings in greater detail, the general layout of strandforming and winding apparatus of FIGS. 1 and 2 is utilized to show themost specific application of the invention. FIGS. 1 and 2 include asource of molten glass, such as a melting unit 10, having an associatedelectrical feeder or bushing 11 from which streams of molten glass flow.The feeder has a plurality of aligned orifices of small dimensions whichform the streams from which the filaments or fibers 12 are then drawn.The feeder is made of high-temperature conducting material such asplatinum and is provided with terminals 20 at opposite ends thereofacross which a potential is applied to supply current of magnitudesufiicient to heat it to the desired attenuating temperature for theglass.

The force of withdrawal of fibers 12 from the material emerging from thefeeder 11 is provided by winding apparatus such as a collet-type winder15 which Winds the strand 14 formed of the fibers 12 onto a collectionor packaging tube 16 in the form of a generally cylindrical package 17.The fibers 12 are usually gathered together by a size-applying andgathering apparatus 13 at a point intermedite the packaging tube 16 andthe feeder 11. Sizing fluid may be supplied to the gathering apparatus13 from an external source, not shown, through a tube 19 disposed abovethe gathering apparatus. After formation, the strand 14 is caused totraverse the collection tube 16 by a spiral wire traverse 18 of thewinder 15.

FIG. 3 illustrates graphically a ramp or slope function, or in otherwords, the stepped manner by which the winder motor speed may be variedwith respect to time to effectively provide fiber uniformity throughouta packaging cycle X. Each step of winder speed variation is matched to apackaging cycle X. At the beginning of a cycle X, the rotational speedof the winder motor and collet is at a maximum, while during the cycle Xthe winder speed is gradually diminished to a minimum which willcompensate for the predetermined linear speed of the strand and fibersdue to build-up of the package. During the period Y on the graph, thecompleted package may be doffed and another collection tube installed onthe collet, or on more advanced winding mechanisms another collet may beindexed into collecting position. During the period Y, the winder speedmay be returned to its initial value at the beginning of a packagingcycle preparatory to the start of another packaging cycle. The change inwinder speed during period Y can be easily effected before the packagingcycle is ready to begin again.

FIG. 4 shows an arrangement adapted to provide uniform fiber diametersby attenuation of a plurality of fibers at a constant linear speed froma feeder. The constant linear speed of attenuation is attained in thisinstance by programming the speed of the winder motor 30 in accordancewith the rate of build-up of the package being wound on winder collet15.

The winder collet is driven by the winder motor 30, which for thepurposes of this embodiment may be a frequency responsive, variablespeed motor. Motor speed control means includes a control motor 40driving a three phase A.C. generator 42 via a magnetic clutch 41, and aramp function generator 43 controlling the magnetic clutch connectionbetween the control motor 40 and the three phase generator 42. For thepurposes of this embodiment, the control motor 40 is preferably aconstant speed synchronous motor. The magnetic clutch 41 isadvantageously adjustable in slip in response to preselected programmedsignals from the ramp function generator 43. The ramp function generatorprovides programmed signals to effect ramp function control of thewinder motor as shown in FIG. 3.

To insure that the winder motor 30 is being driven at the desired speed,there is provided frequency sensing and measuring means for supplyingfrequency signals corresponding to the speed of the motor. The frequencygenerated by the A.C. generator 42 is sampled by a gate 50. The gate 50may be made responsive to pass the sample signal by receipt of signalsfrom a clock timer 44, which may also control the action of the rampfunction generator 43, and a gate timer 51.

A signal from the clock timer 44 will indicate that the speed of thewinder motor 30 is actually being controlled at that time by the rampfunction generator 43. The clock timer 44 may also be set to provide agating signal at the beginning and/or end of a packaging cycle, atpredetermined intervals within the packaging cycle, or throughout thepackaging cycle.

The gate timer 51 may be used to provide a predetermined samplingperiod. Gate timers may be used at a plurality of stations so that thesame frequency measuring apparatus may be time-shared by the pluralityof stations. That is, a master gate timer with a plurality of outputsmay be arranged to successively open gates for sampled signals from aplurality of stations to the frequency measuring apparatus. Similarly, aplurality of gate timers with single outputs may be set to successivelyopen gates connected with different stations. The gate timer 51 may beset to hold the gate open for a predetermined period. In this embodimentthe gate timer would preferably be set to hold the gate open for aminimum of one and one-half cycles of the frequency being measured.Normally, signals from the clock timer and the gate timer must occursimultaneously to open the gate 50.

A counter means 54 is provided which has a count frequency rate that isrelatively high compared to the frequency being measured. For example, acounter frequency within a digital computer may be on the order of fourmegacycles per second. The counter is allowed to count for apredetermined period or a portion of a cycle of the frequency beingmeasured. The accumulated or total count at the end of thispredetermined period or portion of the cycle is a measure of thefrequency being sampled, since the count is a measure of time consumedby that period or the portion of the cycle. If the counter frequency isfour megacycles and the frequency being measured is one hundred twentycycles per second, then the counter would accumulate a total of 332,000counts in a cycle. Therefore, if a counter did accumulate the abovetotal for a cycle, then it would be known that the frequency of thesample being measured was one hundred twenty cycles per second.Similarly, if the counter accumulated half the above total in half acycle, then the frequency would still be known to be one hundred twentycycles per second. Other fractional ratios and multiples thereof or ofwhole cycles may similarly be used to provide a measure of the frequencybeing sampled.

In order to use the counting system, the apparatus must be operative toselect a known portion or whole cycle or multiple of cycles of thefrequency being measured. Means for selecting a predetermined period ora portion of a cycle in this embodiment include a squaring circuit 52,which receives the sample and converts it to a substantially squarewave, and a cross-over signal generator, while a number of means may beused to mark the be ginning and end of a predetermined period or of aportion of a cycle, one of the best suited for this invention is toutilize a circuit which derives a signal from a square wave as itreverses polarity (or crosses over the zero amplitude level) at thehalf-cycle mark. The half-cycle signal may be used as a pulse to resetthe counter 54 and initiate a new counting cycle.

If a whole cycle, or multiples of the half cycle is desired as theportion or period for counting, the cross-over signal generator mayinclude a combination of flip-flops or another counter so that apredetermined number of crossovers must occur before the reset pulse isapplied to the main counter 54. The use of a number of crossovers to setthe period for counting may be useful when the difference or ratiobetween the count frequency and the measured frequency is not so large.The counter 54 may start accumulating a count from the start of itsreceipt of the measured frequency signal from the gate circuit 50 untilthe first reset signal is received from the cross-over generator 53.However, it is not known whether this constitutes the predeterminedportion or period required for measurement.

To determine whether or not the correct predetermined period haselapsed, a number of approaches may be used. First, the counter 54 canbe made responsive only to the cross-over of the frequency beingmeasured. Thus, the counter would be responsive to read out only after afirst reset signal is followed by a counting period and a second resetsignal. This may be accomplished by placing a gate 61 between the outputof a counter memory 70 receiving the output of the counter 54 and atranslator 62 and frequency readout 63 section.

Gate 61 may be made to open in response to a first and second resetsignals which are fed through a circuit such as a flip-flop 60 whichpasses only every other signal. The count stored in the counter memory70 may then be passed through gate 61 to a translator 62 section whichtranslates the accumulated count to the correct frequency, whichfrequency is then shown in the frequency readout 63. It would bedesirable in this instance to provide the counter memory 70 with adelayed reset signal via delay circuit 72 from the cross-over generator53 to clear the counter memory for the next measurement.

As a second method of determining whether the correct period has passed,a count accumulated in the counter 54 before a reset signal, is storedin the counter memory 70. The next count is then compared to the countstored in the memory 70, for example by a subtraction unit 71. If thecounts are identical or within a predetermined tolerance, then the twoperiods of counting must have been substantially identical and thepredetermined period requirement is satisfied. The accumulated count foreither period or the total for both periods may then be used as anexpression of the frequency being measured. If the counts are notidentical or not within a tolerance, then the comparison of successiveperiods is continued until the counts are within the tolerance.

The need for a tolerance sometimes arises if the components in thesquaring circuit 52 are such that the squaring circuit is unable to makethe leading edges of the square waves sufficiently vertical. If a slopeis left in the leading edge of the square wave, the timing of the readsignals from the cross-over generator 53 may be slightly off.

Once the sampled frequency has been measured the result may be utilizedto correct the signal supplied by the ramp function generator 43, ifthere is a variance from the desired frequency being supplied to thewinder motor 30.

A first method of using the sampled frequency is to compare the sampledfrequency from the counter memory 70 with a frequency supplied from aprogrammed memory 80. In this instance there is no requirement toconvert the count in the counter memory 70 since the programmed memorymay supply the comparison frequency in the form of a count. It will benoted that the programmed memory 80 may be controlled by the clock timer44 controlling the ramp function generator 43 so that the comparisonfrequency issued by the programmed memory 80 is the correct one for thatportion of the ramp function cycle. If the measured frequency and theprogrammed frequency counts are the same or within a tolerance, nocorrection signal is provided by the comparing circuit 81 to the rampfunction generator 43. If there is a difference, a signal correspondingto the difference is supplied to the ramp function generator 43 toprovide a correction in the control of the magnetic clutch 41.

A second method of using the sampled frequency is to provide a signalfrom the counter memory through a gate 75 directly to the ramp functiongenerator 43 for internal comparison with a preselected program in theramp function generator 43. Gate 75 may be opened to pass the signalfrom the counter memory 70 in response to a signal from a tolerance unit74. The tolerance unit 74 provides the gating signal in response to asubtraction readout 73 from the subtraction unit 71 which is within theprescribed tolerance when successive periods of counting are beingcompared.

Other methods for comparing and correcting other than those set forthabove may be utilized within the spirit and scope of this invention. Theswitches are shown in the various leads so that a particular method maybe selected.

Since differences are calculated between successive periods, the circuitof FIG. 4 may also be used to measure the rate of change in a frequencybeing sensed.

FIG. 5 illustrates graphically a ramp or slope function, or in otherwords, the stepped manner by which feeder temperature may be varied withrespect to time to effectively provide fiber uniformity throughout thepackaging cycle. Each step of temperature variation is matched to thepackaging cycle X. At the beginning of the cycle X, the feedertemperature is at a minimum while during the cycle it is graduallyincreased to a maximum which will compensate for the increased speed dueto build-up at the end of the cycle.

During the period Y in FIG. 5, While the package is being dotted andanother collection tube is being installed on the collet (or on somewinding mechanisms another collet is being indexed into place), thetemperature of the feeder is reduced to its initial value at thebeginning of the cycle preparatory to the start of another packagingcycle X. It has been found that this reduction in temperature can beeffected in a period of very short duration by cutting back on currentflow through the feeder. Because of the high temperature differentialbetween the feeder and the surrounding atmosphere, the period requiredto effect temperature reduction is a matter of mere seconds and issufficiently rapid not to be a retardent to start-up of a subsequentpackaging cycle. In other words, the reduction in temperature can beeffected with time to spare in the period usually required to provide anew collection tube for making a new package.

FIG. 6 shows an electrical power circuit and associated controls forsupply of energy to heat the feeder 11. Broadly, the power circuitincludes a saturable reactor 122 in series with a power transformer forthe feeder. The feeder is connected by way of its terminals across thesecondary winding 124 of the power transformer while the primary of thewinding 123 of the transformer is connected serially with the saturablereactor 122. The series circuit is connected to a suitable power linesource L1, L2 such, for example, as a 440 volt, 60 cycle line throughcontacts of a line circuit breaker and over a pair of suitablyfuse-protected circuit leads.

Current regulating controls for the power circuit may be provided byconventional-type temperature-sensing and regulating unit 129, such as aunit of the type well known to the instrument trade as a Wheelco unitwhich can be arranged to operate in conjunction with atemperaturesensing thermocouple 126. This unit operates to sense thetemperature of the feeder by way of the thermocouple 126 and to indicatethe temperature signal at a meter provided with means for presetting thetemperature desired. As the temperature signal fed to the unit variesfrom a preset value, the unit functions to supply a corrected signal tothe power circuit by way of the saturable reactor to establish thecurrent flow for the temperature desired. However, the regulating unitnot only receives the signal from the thermocouple 126, but also anauxiliary signal corresponding in effect to a false temperature signalsupplied by unit 127.

The saturable-core reactor 122 has an associated directcurrent windingwhich when energized builds up the flux concentration in the reactor ina characteristic manner according to its B-H curve. Energy for the D.C.winding 130 is supplied from the temperature regulating unit 129. Whenthe flux concentration in the saturable-eore reactor 122 is high on theB-H curve, such as at a point just below the knee of the curve, theinductive reactance of the reactor is at a minimum and the currentsupplied to the transformer by way of its primary is correspondingly ata maximum. When, however, the direct-current flow in the winding 130 issomewhat smaller, such that the flux concentration in the reactor dwellsin the region of a point considerably below the knee of the curve, theinductive reactance of the reactor is more appreciable and the currentflow in the transformer primary is accordingly lower. Thus, the amountof direct-current flowing in the winding 130 determines the magnitude ofthe reactance in series with the transformer and consequently determinesthe amount of electrical energy supplied to establish the temperature offeeder 11.

As indicated previously, it has been found that by causing a gradualincrease in the temperature of the feeder as increases in speed ofattenuation of fibers occur permits production of fibers of uniformdiameter throughout each packaging cycle for each package wound. Thatis, as the speed of attenuation increase due to package build-up, agradual increase in temperature of the feeder at a matched rate, resultsin establishment of compensating variations in the attenuating factorsto permit production of fibers uniform in diameter within a very closetolerance. On viewing the operation more fundamentally, it appears thatthe progressive increase in temperature of the glass in actuality causesthe glass to flow more freely from the feeder. Thus, more moltenmaterial is made available as the speed of attenuation increases tomaintain the diameter of the glass fibers uniform.

The gradual build up of temperature can be accomplished by supplying afalse temperature signal to the regulating unit 129 from the unit 127along with the temperature signal supplied thereto by the thermocouple126. The unit 127 is connected to the regulating unit 129 in series withthe thermocouple and is arranged to oppose the thermocouple signal as itincreases, to falsely indicate to the unit 129 that the temperature ofthe feeder is gradually diminishing. That is, the regulating unitreceives a false temperature signal which causes it to allow the currentflow through the feeder to gradually increase and consequently effect agradual increase in temperature of the feeder.

More than one type of circuit arrangement might be adopted to providethis false signal. Circuit arrangements suitable for the falseproduction of signals such as indicated in block diagram form at 127 inFIG. 6 are shown in US. Pat. No. 3,126,268, issued Mar. 24, 1964, to C.L. Roberson. Such circuits comprise means for supplying programmedauxiliary signals to the control means for the heating of the moltenbody in the feeder 11 for variation of the temperature of the moltenbody in the feeder means at a rate matched to variations in the rate ofattenuation of the streams in response to the package buildup. Asillustrated in the cited U.S. patent, above, such a circuit may be avacuum tube circuit which prolongs the charge characteristics of aresistance-capacitor circuit to provide a ramp-function or graduallyincreasing directcurrent signal arranged to oppose the thermocouplesignal. The ramp-function signal is preferably initiated responsive toclosure of a switch 128 which is suitably associated with the windingapparatus for actuation when the winder begins a package winding cycle.The switch may be conveniently associated with the winder traversemechanism to operate in this manner. The switch 128 can also be readilyarranged to be opened automatically and the winding apparatus stoppedautomatically when the package is built to full size such as may bedetermined by winding for a given period, thus completing a packagingcycle.

In view of the minute diameters of fibers being attained with newprocesses, it is highly desirable to be able to check whether or not thetemperature of the molten body is responding correctly to theramp-function being provided by the unit 127. In order to accomplishthis, there is provided a means for sensing the temperature of themolten body and generating a frequency signal in which the frequencysignal varies in proportion to the variation of the temperature beingsensed. In FIG. 6, this is accomplished by providing a frequencygenerating or oscillator circuit 140 which includes temperaturesensitive components such as crystals 141 and 142. One of thetemperature sensitive components 142 may be thermally isolated or heldat a predetermined fixed temperature. The other temperature sensitivecomponent 141 is disposed in heat sensing relationship with the moltenbody held in feeder 11. Because of the differences in temperature, thecomponents 141 and 142 will generate or pass different frequencies. Acomparison or differential circuit 143 is utilized to compare thesefrequencies and to provide an output to a frequency measuring unit 144which is variable in proportion to the variation of the temperature ofthe molten body.

The frequency measuring unit 144 includes means for measuring thefrequency such as illustrated in FIG. 4 and provides an output to acomparing circuit 145. The comparing circuit 145 also receives an inputfrom a preselected standard 146. This preselected standard may be in theform of a count of a frequency, or in comparable form to the inputreceived by the comparing circuit 145 from the frequency measuring unit144. The preselected standard unit 146 is preferably stepped in timeaccording to the portion of the packaging cycle being measured. This maybe accomplished by reference to or connection with the regulating unit129. Alternatively, the switching means 128 may be utilized to connectthe preselected standard unit 146 to be operative to provide asuccessive series of standards comparable to that portion of the cyclebeing measured. A clock timer may hold the operation of the standardunit 146 in step with the packaging cycle. As a further alternative, thepreselected standard unit 146 may provide an input to the comparingcircuits 145 from a computer memory which is programmed to supply thestandards in accordance with the time elapsed of the packaging cyclebeing sensed.

The comparing circuit 145 compares the signals received from thefrequency measuring unit 144 and the preselected standard unit 146. Ifthere is a variation from the standard, a corrective signal is appliedfrom the comparing circuit 145 to the control circuit. As shown in FIG.6, this corrective signal may be connected to the false temperaturesignal being supplied to the unit 129. Other suitable connections mayalso be made in correcting the programmed auxiliary signals inaccordance with the difference between the preselected standard and theactual results of the control means at that time.

Thus, it can be seen that extremely close control can be accorded to theproduction of fibers. This is particularly important since the size ofthe fibers produced are now in diameters of a range very, very close tothe minimum diameter attainable. That is, if the temperature of themolten material in the feeder 11 or the speed of the attenuating meansis varied a small degree past the tolerance limits set by the controlswhen producing fibers of a minimum diameter, the result may be breakouts of the fiber producing apparatus causing shut downs and loss ofproduction. Therefore, it is extremely important that such variableconditions in the production of fibers be very closely controlled. Eventhough closely controlled, the variable conditions may be caused to varyby supply line surges, changes in ambient temperature conditions, etc.

Referring to FIG. 7, there is illustrated another embodiment of thecondition sensing and controlling apparatus of this invention whichcomprises means for sensing a fluid flow variable condition. Theapparatus of FIG. 7 includes means operative to be driven by the fluidflow to produce a frequency signal in which the frequency of the signalvaries in proportion to the rate of flow of the fluid. Such fluid flowresponsive means may be a propeller or turbine means 150. The propelleror turbine means may be mechanically or electrically linked with a meansfor producing a frequency signal. Further, the propeller or turbinemovement may be sensed by vibration sensitive means which will translatethe signal received into a frequency signal proportional to the flow offluid.

Referring to FIG. 8, there is shown apparatus in which the variablecondition being measured is particle flow. The sensing and generatingmeans in this instance includes a frequency generator having anadjustable component 161, which may be in this instance an adjustablecapacitor or an adjustable inductance in an oscillator circuit, forvarying the frequency output. The means responsive to particle flow inthis instance may include weighing means having an indicating means 166.The indicating means 166 may be linked to adjust the adjustablecomponent 161 to vary the frequency signal output from the unit 160 inproportion to the particle flow. The weighing means 165 may beresponsive to the weight of particles flowing or being moved along aconveyor having a weighing section.

Referring to FIG. 9, there is illustrated apparatus in which thevariable condition being measured is pressure, and in which the sensingand generating means includes means 170 for sensing the pressure beingmeasured and includes an indicating means such as a movable diaphragm171. Again a frequency generating means may be utilized having anadjustable component 176, which may be an adjustable capacitor orinductance in an oscillator circuit, responsive to the indicating means171 for varying the output frequency of the generating means 175. Thediaphragm means may be mechanically linked to the adjustable component176.

Although direct linkages have been shown in FIGS. 7, 8 and 9, it is tobe noted that various optical and other indicating systems which areinfinitely more sensitive to minute variations may be utilized tocontrol the output of the frequency generating means. 'If a mechanicallinkage is not sufficiently refined to record minute variations andcause the variation in frequency output desired, optical or lightsystems may be utilized which effect the output or performance of lightsensitive components, including many in the transistor field today, toproduce the desired minute variations.

In FIGS. 7 to 9 the frequency signal produced may be measured by theapparatus disclosed hereinbefore to provide measurement of the variablecondition. The measurement of the variable condition may be used toalter the 1 1 condition directly or to alter a programmed auxiliarysignal which is controlling the variable condition.

In conclusion, it should be noted that variations to the apparatustaught in this invention may be made to attain the desired results.However, the embodiments disclosed and described herein are meant to beillustrative only and not limiting in any sense. The embodimentsdescribed serve merely to illustrate the spirit and scope of theinvention.

I claim:

1. Fiber producing apparatus comprising in combination feeder means forcontaining a molten body of thermoplastic material, means for heating amolten body in said feeder means, control means for said heating means,rotary winder means for attenuating streams of molten material from saidfeeder into continuous fibers and for winding said fibers into apackage, a temperature measuring device included in said control meansarranged to supply signals to regulate said heating means formaintenance of a given temperature of a molten body in said feedermeans, means for supplying programmed auxiliary signals to said controlmeans for variation of the temperature of a molten body in said feedermeans at a rate matched to variations in the rate of attenuation of saidstreams in response to package build up, means for sensing thetemperature of said molten body and generating a frequency signal inwhich the frequency of the signal varies in proportion to the variationof the temperature being sensed, means for selecting a predeterminedperiod of the frequency signal, counter means responsive to saidselecting means adapted to count at a predetermined frequency duringsaid selected period, said counting frequency being higher than thefrequency of the signal frequency being measured, means for comparingthe measured frequency count with a preselected standard, and meansresponsive to said comparing means for effecting correction of saidcontrol means.

2. Apparatus for producing glass fibers comprising in combination feedermeans for receiving a body of molten glass and forming streams of glassfor attenuation into fibers, means for heating said body of glass beforestream formation, control means for said heating means, means forattenuating said streams into fibers, said control means includingtemperature measuring means for supplying signals to regulate saidheating means for maintenance of said molten body at a preselectedtemperature, means for supplying programmed auxiliary signals to saidcontrol means for variation of the temperature of said molten body at arate matched to variation in the rate of attenuation, means for sensingthe temperature of said molten body and generating a frequency signal inwhich the frequency of the signal varies in response to the variation ofthe temperature being sensed, means for selecting a predetermined periodof the frequency signal, counter means responsive to said selectingmeans adapted to count at a predetermined frequency during said selectedperiod, said counting frequency being higher than the frequency of thesignal frequency being measured, means for comparing the measuredfrequency count with a preselected standard, and means responsive tosaid comparing means for effecting correction of said control means.

3. Aparatus for producing glass fibers comprising feeder means forreceiving a body of molten glass and forming streams of glass forattenuation into fibers; means for heating said body of glass beforestream formation; and control means for said heating means includingmeans for generating a frequency signal which is variable in proportionto the variation of the temperature of the molten glass, means forselecting a known portion of the cyclic variation of said temperaturefrequency signal, counter means responsive to said known portionselecting means for counting at a predetermined frequency during saidselected known period to provide a measure of the temperature of saidglass, the counting frequency being higher than said temperaturefrequency signal, and means responsive to said counter means forregulating the amount of heat supplied to said glass.

References Cited UNITED STATES PATENTS 3,047,647 7/1962 Harkins et al.651 1W 3,265,476 8/1966 Roberson 651 3,308,291 3/1967 Kruse 324-79D3,471,278 10/1969 Griem 652 S. LEON BASHORE, Primary Examiner R. L.LINDSAY, 1a., Assistant Examiner US. Cl. X.R.

